Deploying Carrier-Grade Business Services over Cable Networks

By Scott Sumner, Accedian Networks

With proven success in the residential triple-play market establishing MSOs as an emerging leader in telecom services, cable operators are turning to business services for continued growth. It's a great fit. With newly acquired telephony expertise and fiber-rich networks with a half-mile of 80% of U.S. businesses, cable operators are well positioned to capture the underserved small and medium business (SMB) communications market.

Independent research by Comcast and Time Warner Cable tally 2.8 million SMBs in the U.S., accounting for $15 billion in telecom spending in 2007. Much of this market is served by inflexible ILECs and CLECs, which consistently focus on larger enterprises at the expense of SMB service and support.

Requirements for Business Services

SMBs are widespread adopters of IP-based communications solutions that help them compete with larger competitors within limited telecom budgets. An effective SMB business services portfolio includes multi-line phone service, Internet access, remote storage and backup, video/Web conferencing as well as reliable VPN services. This is a challenging lineup to deliver considering the mix of best-effort, real-time and business critical applications each with different performance requirements.

MSOs are addressing these challenges by turning to Ethernet. All major U.S. MSOs, including Comcast, Time Warner Cable, Charter, Cox and Cablevision are members of the Metro Ethernet Forum (MEF), an organization developing the standards that enable carrier-grade Ethernet services. It's a natural fit for cable operators. Carrier Ethernet takes the notion of the triple-play to the next level, providing a framework to deliver dozens of IP-based and emulated TDM services over a single managed connection.

Creating Ethernet Services

The power of Carrier Ethernet connectivity is its ability to concurrently carry multiple services at different rates and priorities to multiple destinations. This multitasking functionality is provided over Ethernet virtual circuits (EVCs), established between service endpoints to efficiently separate and transport traffic over shared access and core networks.

EVCs, which can be point-to-point or multipoint, are created by a technique known as service mapping - a method of tagging application and customer-specific traffic as it enters the provider's network. Service mapping establishes EVCs with a specific VLAN ID, class of service (priority) and bandwidth profile that defines throughput and burst performance.

The endpoints of the EVC where the service effectively hands off from the MSO's network to the customer's network are known as the service demarcation (demarc) points. A mix of traffic processing capabilities at the demarc can help maintain EVC performance. The most common include:

• Bandwidth policing - also known as rate limiting, bandwidth policing protects the MSO's network from excess traffic by regulating throughput per-flow or EVC before it enters the network
• Traffic filtering - selectively blocks traffic based on granular packet filtering criteria to protect management VLANs and prevent unwanted and malicious traffic from flooding the network
• Traffic shaping - prioritizes critical, real-time traffic while buffering and queuing lower-priority packets during bursty periods; reduces bandwidth demands and accelerates services by reducing network overhead

Managing Ethernet Services

Although cost-efficient from a capital perspective, Ethernet services can quickly become expensive to deploy and maintain without effective end-to-end management. A number of established Ethernet Operations, Administration and Maintenance (OAM) standards have been defined that enable cost-efficient service provisioning, remote troubleshooting (including loopback testing) and fault isolation for the service, connectivity and access-link layers. The most common OAM specifications include the IEEE's 802.1ag & 802.3ah, and ITU-T Y.1731. End-to-end OAM can be established using compliant access platforms or by deploying OAM-enabling Ethernet network interface devices (EtherNIDs) at service demarc points.

Packet Performance Assurance

Defining Ethernet services with specific performance requirements allows MSOs to offer various service levels (e.g., standard, premium and critical) backed by revenue driving service level agreements (SLAs). However, changing traffic conditions, new services, network congestion and configuration errors are some of the many reasons why a service may perform sub-par. Just as SLAs allow providers to charge service premiums, SLA violations often mean financial penalties to the service provider.

Assuring the performance of Ethernet services requires:

• The ability to monitor performance in-service without disturbing customer traffic or waiting for maintenance windows to test, since worst-case traffic conditions occur at peak hours
• An end-to-end view of the service, from demarc-to-demarc
• The ability to precisely measure common SLA performance KPIs: throughput, one-way delay and jitter, availability and packet loss

The most cost-effective solutions combine a centralized monitoring system with intelligent demarcation devices that can analyze 100% of the customer traffic flowing through them at the edge, generate and analyze test streams and collect usage statistics without affecting customer traffic. Put together, these capabilities create a kind of "SLA-meter," allowing MSOs to back up their services with assured SLAs, and report this to their customers.

Scott Sumner is VP of marketing at Accedian Networks.

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